Implementation of Pascal's Triangle with Perl and Moose

Probably not the best way to do it, but I thought I would give it a hack:

#!/usr/bin/perl

package Row;

use Moose;

has triangle => (
    is  => 'ro',
    isa => 'Triangle',
);

has prev => (
    is        => 'ro',
    isa       => 'Row',
);

has members => (
    is         => 'rw',
    isa        => 'ArrayRef[Int]',
    lazy_build => 1,
);

sub _build_members {
    my $self = shift;
    
    return [1] unless $self->prev;
    
    my @prev = @{ $self->prev->members };
    
    my @values = (1);
    
    for(my $i = 0; $i < ( scalar(@prev) - 1 ); $i++) {
        my $c = $prev[ $i ];
        my $n = $prev[ $i + 1 ] || 1;
        
        push @values, $c + $n;
    }
    
    push @values, 1;
    
    return \@values;
}

sub print {
    my $self = shift;
    print join ' ', @{ $self->members },"\n";
    return $self;
}

__PACKAGE__->meta->make_immutable;

no Moose;

package Triangle;

use Moose;

has rows => (
    is      => 'rw',
    isa     => 'ArrayRef[Row]',
    default => sub { [ Row->new({}) ] },
);

sub first {
    my $self = shift;
    return $self->rows->[0];
}

sub last {
    my $self = shift;
    return $self->rows->[ $#{ $self->rows } ];
}

sub next {
    my $self = shift;
    my $row = Row->new( prev => $self->last );
    push @{ $self->rows }, $row;
    return $self->last;
}

__PACKAGE__->meta->make_immutable;

package main;

die "Usage: $0 \n"
    unless $ARGV[0] > 1;
    
    
my $t = Triangle->new;

$t->next->prev->print foreach(1..$ARGV[0]);